… | |
… | |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use Convert::BER::XS ':all'; |
7 | use Convert::BER::XS ':all'; |
8 | |
8 | |
9 | my $ber = ber_decode $buf |
9 | my $ber = ber_decode $buf, $Convert::BER::XS::SNMP_PROFILE |
10 | or die "unable to decode SNMP v1/v2c Message"; |
10 | or die "unable to decode SNMP message"; |
11 | |
11 | |
12 | # the above results in a data structure consisting of (class, tag, |
12 | # The above results in a data structure consisting of |
|
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13 | # (class, tag, # constructed, data) |
13 | # constructed, data) tuples. here is such a message, SNMPv1 trap |
14 | # tuples. Below is such a message, SNMPv1 trap |
14 | # with a cisoc mac change notification |
15 | # with a Cisco mac change notification. |
|
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16 | # Did you know that Cisco is in the news almost |
|
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17 | # every week because of some backdoor password |
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18 | # or other extremely stupid security bug? |
15 | |
19 | |
16 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, |
20 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, |
17 | [ |
21 | [ |
18 | [ ASN_UNIVERSAL, ASN_INTEGER32, 0, 0 ], # snmp version 1 |
22 | [ ASN_UNIVERSAL, ASN_INTEGER, 0, 0 ], # snmp version 1 |
19 | [ ASN_UNIVERSAL, 4, 0, "public" ], # community |
23 | [ ASN_UNIVERSAL, 4, 0, "public" ], # community |
20 | [ ASN_CONTEXT, 4, 1, # CHOICE, constructed |
24 | [ ASN_CONTEXT, 4, 1, # CHOICE, constructed - trap PDU |
21 | [ |
25 | [ |
22 | [ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.2" ], # enterprise oid |
26 | [ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.2" ], # enterprise oid |
23 | [ ASN_APPLICATION, 0, 0, "\x0a\x00\x00\x01" ], # SNMP IpAddress, 10.0.0.1 |
27 | [ ASN_APPLICATION, SNMP_IPADDRESS, 0, "10.0.0.1" ], # SNMP IpAddress |
24 | [ ASN_UNIVERSAL, ASN_INTEGER32, 0, 6 ], # generic trap |
28 | [ ASN_UNIVERSAL, ASN_INTEGER, 0, 6 ], # generic trap |
25 | [ ASN_UNIVERSAL, ASN_INTEGER32, 0, 1 ], # specific trap |
29 | [ ASN_UNIVERSAL, ASN_INTEGER, 0, 1 ], # specific trap |
26 | [ ASN_APPLICATION, ASN_TIMETICKS, 0, 1817903850 ], # SNMP TimeTicks |
30 | [ ASN_APPLICATION, SNMP_TIMETICKS, 0, 1817903850 ], # SNMP TimeTicks |
27 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # the varbindlist |
31 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # the varbindlist |
28 | [ |
32 | [ |
29 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # a single varbind, "key value" pair |
33 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # a single varbind, "key value" pair |
30 | [ |
34 | [ |
31 | [ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.1.1.8.1.2.1" ], # the oid |
35 | [ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.1.1.8.1.2.1" ], |
32 | [ ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "...data..." # the value |
36 | [ ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "...data..." # the value |
33 | ] |
37 | ] |
34 | ] |
38 | ] |
35 | ], |
39 | ], |
36 | ... |
40 | ... |
… | |
… | |
38 | # let's decode it a bit with some helper functions |
42 | # let's decode it a bit with some helper functions |
39 | |
43 | |
40 | my $msg = ber_is_seq $ber |
44 | my $msg = ber_is_seq $ber |
41 | or die "SNMP message does not start with a sequence"; |
45 | or die "SNMP message does not start with a sequence"; |
42 | |
46 | |
43 | ber_is $msg->[0], ASN_UNIVERSAL, ASN_INTEGER32, 0 |
47 | ber_is $msg->[0], ASN_UNIVERSAL, ASN_INTEGER, 0 |
44 | or die "SNMP message does not start with snmp version\n"; |
48 | or die "SNMP message does not start with snmp version\n"; |
45 | |
49 | |
46 | # message is SNMP v1 or v2c? |
50 | # message is SNMP v1 or v2c? |
47 | if ($msg->[0][BER_DATA] == 0 || $msg->[0][BER_DATA] == 1) { |
51 | if ($msg->[0][BER_DATA] == 0 || $msg->[0][BER_DATA] == 1) { |
48 | |
52 | |
… | |
… | |
51 | my $trap = $msg->[2][BER_DATA]; |
55 | my $trap = $msg->[2][BER_DATA]; |
52 | |
56 | |
53 | # check whether trap is a cisco mac notification mac changed message |
57 | # check whether trap is a cisco mac notification mac changed message |
54 | if ( |
58 | if ( |
55 | (ber_is_oid $trap->[0], "1.3.6.1.4.1.9.9.215.2") # cmnInterfaceObjects |
59 | (ber_is_oid $trap->[0], "1.3.6.1.4.1.9.9.215.2") # cmnInterfaceObjects |
56 | and (ber_is_i32 $trap->[2], 6) |
60 | and (ber_is_int $trap->[2], 6) |
57 | and (ber_is_i32 $trap->[3], 1) # mac changed msg |
61 | and (ber_is_int $trap->[3], 1) # mac changed msg |
58 | ) { |
62 | ) { |
59 | ... and so on |
63 | ... and so on |
60 | |
64 | |
61 | # finally, let's encode it again and hope it results in the same bit pattern |
65 | # finally, let's encode it again and hope it results in the same bit pattern |
62 | |
66 | |
63 | my $buf = ber_encode $ber; |
67 | my $buf = ber_encode $ber, $Convert::BER::XS::SNMP_PROFILE; |
64 | |
68 | |
65 | =head1 DESCRIPTION |
69 | =head1 DESCRIPTION |
66 | |
70 | |
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71 | WARNING: Before release 1.0, the API is not considered stable in any way. |
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72 | |
67 | This module implements a I<very> low level BER/DER en-/decoder. |
73 | This module implements a I<very> low level BER/DER en-/decoder. |
68 | |
74 | |
69 | If is tuned for low memory and high speed, while still maintaining some |
75 | It is tuned for low memory and high speed, while still maintaining some |
70 | level of user-friendlyness. |
76 | level of user-friendlyness. |
71 | |
77 | |
72 | Currently, not much is documented, as this is an initial release to |
78 | =head2 EXPORT TAGS AND CONSTANTS |
73 | reserve CPAN namespace, stay tuned for a few days. |
79 | |
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80 | By default this module doesn't export any symbols, but if you don't want |
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81 | to break your keyboard, editor or eyesight with extremely long names, I |
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82 | recommend importing the C<:all> tag. Still, you can selectively import |
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83 | things. |
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84 | |
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85 | =over |
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86 | |
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87 | =item C<:all> |
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88 | |
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89 | All of the below. Really. Recommended for at least first steps, or if you |
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90 | don't care about a few kilobytes of wasted memory (and namespace). |
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91 | |
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92 | =item C<:const> |
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93 | |
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94 | All of the strictly ASN.1-related constants defined by this module, the |
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95 | same as C<:const_asn :const_index>. Notably, this does not contain |
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96 | C<:const_ber_type> and C<:const_snmp>. |
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97 | |
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98 | A good set to get everything you need to decode and match BER data would be |
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99 | C<:decode :const>. |
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100 | |
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101 | =item C<:const_index> |
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102 | |
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103 | The BER tuple array index constants: |
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104 | |
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105 | BER_CLASS BER_TAG BER_FLAGS BER_DATA |
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106 | |
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107 | =item C<:const_asn> |
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108 | |
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109 | ASN class values (these are C<0>, C<1>, C<2> and C<3>, respectively - |
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110 | exactly thw two topmost bits from the identifier octet shifted 6 bits to |
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111 | the right): |
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112 | |
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113 | ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE |
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114 | |
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115 | ASN tag values (some of which are aliases, such as C<ASN_OID>). Their |
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116 | numerical value corresponds exactly to the numbers used in BER/X.690. |
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117 | |
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118 | ASN_BOOLEAN ASN_INTEGER ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER |
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119 | ASN_OBJECT_DESCRIPTOR ASN_OID ASN_EXTERNAL ASN_REAL ASN_SEQUENCE ASN_ENUMERATED |
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120 | ASN_EMBEDDED_PDV ASN_UTF8_STRING ASN_RELATIVE_OID ASN_SET ASN_NUMERIC_STRING |
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121 | ASN_PRINTABLE_STRING ASN_TELETEX_STRING ASN_T61_STRING ASN_VIDEOTEX_STRING ASN_IA5_STRING |
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122 | ASN_ASCII_STRING ASN_UTC_TIME ASN_GENERALIZED_TIME ASN_GRAPHIC_STRING ASN_VISIBLE_STRING |
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123 | ASN_ISO646_STRING ASN_GENERAL_STRING ASN_UNIVERSAL_STRING ASN_CHARACTER_STRING ASN_BMP_STRING |
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124 | |
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125 | =item C<:const_ber_type> |
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126 | |
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127 | The BER type constants, explained in the PROFILES section. |
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128 | |
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129 | BER_TYPE_BYTES BER_TYPE_UTF8 BER_TYPE_UCS2 BER_TYPE_UCS4 BER_TYPE_INT |
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130 | BER_TYPE_OID BER_TYPE_RELOID BER_TYPE_NULL BER_TYPE_BOOL BER_TYPE_REAL |
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131 | BER_TYPE_IPADDRESS BER_TYPE_CROAK |
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132 | |
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133 | =item C<:const_snmp> |
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134 | |
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135 | Constants only relevant to SNMP. These are the tag values used by SNMP in |
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136 | the C<ASN_APPLICATION> namespace and have the exact numerical value as in |
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137 | BER/RFC 2578. |
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138 | |
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139 | SNMP_IPADDRESS SNMP_COUNTER32 SNMP_UNSIGNED32 SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64 |
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140 | |
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141 | =item C<:decode> |
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142 | |
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143 | C<ber_decode> and the match helper functions: |
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144 | |
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145 | ber_decode ber_is ber_is_seq ber_is_int ber_is_oid |
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146 | |
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147 | =item C<:encode> |
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148 | |
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149 | C<ber_encode> and the construction helper functions: |
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150 | |
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151 | ber_encode ber_int |
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152 | |
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153 | =back |
74 | |
154 | |
75 | =head2 ASN.1/BER/DER/... BASICS |
155 | =head2 ASN.1/BER/DER/... BASICS |
76 | |
156 | |
77 | ASN.1 is a strange language that can be sed to describe protocols and |
157 | ASN.1 is a strange language that can be used to describe protocols and |
78 | data structures. It supports various mappings to JSON, XML, but most |
158 | data structures. It supports various mappings to JSON, XML, but most |
79 | importantly, to a various binary encodings such as BER, that is the topic |
159 | importantly, to a various binary encodings such as BER, that is the topic |
80 | of this module, and is used in SNMP or LDAP for example. |
160 | of this module, and is used in SNMP, LDAP or X.509 for example. |
81 | |
161 | |
82 | While ASN.1 defines a schema that is useful to interpret encoded data, |
162 | While ASN.1 defines a schema that is useful to interpret encoded data, |
83 | the BER encoding is actually somehat self-describing: you might not know |
163 | the BER encoding is actually somewhat self-describing: you might not know |
84 | whether something is a string or a number or a sequence or something else, |
164 | whether something is a string or a number or a sequence or something else, |
85 | but you can nevertheless decode the overall structure, even if you end up |
165 | but you can nevertheless decode the overall structure, even if you end up |
86 | with just a binary blob for the actual value. |
166 | with just a binary blob for the actual value. |
87 | |
167 | |
88 | This works because BER values are tagged with a type and a namespace, |
168 | This works because BER values are tagged with a type and a namespace, |
89 | and also have a flag that says whther a value consists of subvalues (is |
169 | and also have a flag that says whether a value consists of subvalues (is |
90 | "constructed") or not (is "primitive"). |
170 | "constructed") or not (is "primitive"). |
91 | |
171 | |
92 | Tags are simple integers, and ASN.1 defines a somewhat weird assortment of |
172 | Tags are simple integers, and ASN.1 defines a somewhat weird assortment |
93 | those - for example, you have 32 bit signed integers and 16(!) different |
173 | of those - for example, you have one integers and 16(!) different |
94 | string types, but there is no unsigned32 type for example. Different |
174 | string types, but there is no Unsigned32 type for example. Different |
95 | applications work around this in different ways, for example, SNMP defines |
175 | applications work around this in different ways, for example, SNMP defines |
96 | application-specific Gauge32, Counter32 and Unsigned32, which are mapped |
176 | application-specific Gauge32, Counter32 and Unsigned32, which are mapped |
97 | to two different tags: you can distinguish between Counter32 and the |
177 | to two different tags: you can distinguish between Counter32 and the |
98 | others, but not between Gause32 and Unsigned32, without the ASN.1 schema. |
178 | others, but not between Gause32 and Unsigned32, without the ASN.1 schema. |
99 | |
179 | |
… | |
… | |
102 | =head2 DECODED BER REPRESENTATION |
182 | =head2 DECODED BER REPRESENTATION |
103 | |
183 | |
104 | This module represents every BER value as a 4-element tuple (actually an |
184 | This module represents every BER value as a 4-element tuple (actually an |
105 | array-reference): |
185 | array-reference): |
106 | |
186 | |
107 | [CLASS, TAG, CONSTRUCTED, DATA] |
187 | [CLASS, TAG, FLAGS, DATA] |
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188 | |
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189 | For example: |
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190 | |
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191 | [ASN_UNIVERSAL, ASN_INTEGER, 0, 177] # the integer 177 |
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192 | [ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "john"] # the string "john" |
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193 | [ASN_UNIVERSAL, ASN_OID, 0, "1.3.6.133"] # some OID |
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194 | [ASN_UNIVERSAL, ASN_SEQUENCE, 1, [ [ASN_UNIVERSAL... # a sequence |
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195 | |
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196 | To avoid non-descriptive hardcoded array index numbers, this module |
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197 | defines symbolic constants to access these members: C<BER_CLASS>, |
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198 | C<BER_TAG>, C<BER_FLAGS> and C<BER_DATA>. |
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199 | |
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200 | Also, the first three members are integers with a little caveat: for |
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201 | performance reasons, these are readonly and shared, so you must not modify |
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202 | them (increment, assign to them etc.) in any way. You may modify the |
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203 | I<DATA> member, and you may re-assign the array itself, e.g.: |
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204 | |
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205 | $ber = ber_decode $binbuf; |
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206 | |
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207 | # the following is NOT legal: |
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208 | $ber->[BER_CLASS] = ASN_PRIVATE; # ERROR, CLASS/TAG/FLAGS are READ ONLY(!) |
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209 | |
|
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210 | # but all of the following are fine: |
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211 | $ber->[BER_DATA] = "string"; |
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212 | $ber->[BER_DATA] = [ASN_UNIVERSAL, ASN_INTEGER, 0, 123]; |
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213 | @$ber = (ASN_APPLICATION, SNMP_TIMETICKS, 0, 1000); |
108 | |
214 | |
109 | I<CLASS> is something like a namespace for I<TAG>s - there is the |
215 | I<CLASS> is something like a namespace for I<TAG>s - there is the |
110 | C<ASN_UNIVERSAL> namespace which defines tags common to all ASN.1 |
216 | C<ASN_UNIVERSAL> namespace which defines tags common to all ASN.1 |
111 | implementations, the C<ASN_APPLICATION> namespace which defines tags for |
217 | implementations, the C<ASN_APPLICATION> namespace which defines tags for |
112 | specific applications (for example, the SNMP C<Unsigned32> type is in this |
218 | specific applications (for example, the SNMP C<Unsigned32> type is in this |
113 | namespace), a special-purpose context namespace (C<ASN_CONTEXT>, used e.g. |
219 | namespace), a special-purpose context namespace (C<ASN_CONTEXT>, used e.g. |
114 | for C<CHOICE>) and a private namespace (C<ASN_PRIVATE>). |
220 | for C<CHOICE>) and a private namespace (C<ASN_PRIVATE>). |
115 | |
221 | |
116 | The meaning of the I<TAG> depends on the namespace, and defines a |
222 | The meaning of the I<TAG> depends on the namespace, and defines a |
117 | (partial) interpretation of the data value. For example, right now, SNMP |
223 | (partial) interpretation of the data value. For example, SNMP defines |
118 | application namespace knowledge ix hardcoded into this module, so it |
224 | extra tags in the C<ASN_APPLICATION> namespace, and to take full advantage |
119 | knows that SNMP C<Unsigned32> values need to be decoded into actual perl |
225 | of these, you need to tell this module how to handle those via profiles. |
120 | integers. |
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121 | |
226 | |
122 | The most common tags in the C<ASN_UNIVERSAL> namespace are |
227 | The most common tags in the C<ASN_UNIVERSAL> namespace are |
123 | C<ASN_INTEGER32>, C<ASN_BIT_STRING>, C<ASN_NULL>, C<ASN_OCTET_STRING>, |
228 | C<ASN_INTEGER>, C<ASN_BIT_STRING>, C<ASN_NULL>, C<ASN_OCTET_STRING>, |
124 | C<ASN_OBJECT_IDENTIFIER>, C<ASN_SEQUENCE>, C<ASN_SET> and |
229 | C<ASN_OBJECT_IDENTIFIER>, C<ASN_SEQUENCE>, C<ASN_SET> and |
125 | C<ASN_IA5_STRING>. |
230 | C<ASN_IA5_STRING>. |
126 | |
231 | |
127 | The most common tags in SNMP's C<ASN_APPLICATION> namespace |
232 | The most common tags in SNMP's C<ASN_APPLICATION> namespace are |
128 | are C<SNMP_IPADDRESS>, C<SNMP_COUNTER32>, C<SNMP_UNSIGNED32>, |
233 | C<SNMP_COUNTER32>, C<SNMP_UNSIGNED32>, C<SNMP_TIMETICKS> and |
129 | C<SNMP_TIMETICKS>, C<SNMP_OPAQUE> and C<SNMP_COUNTER64>. |
234 | C<SNMP_COUNTER64>. |
130 | |
235 | |
131 | The I<CONSTRUCTED> flag is really just a boolean - if it is false, the |
236 | The I<FLAGS> value is really just a boolean at this time (but might |
132 | the value is "primitive" and contains no subvalues, kind of like a |
237 | get extended) - if it is C<0>, the value is "primitive" and contains |
133 | non-reference perl scalar. IF it is true, then the value is "constructed" |
238 | no subvalues, kind of like a non-reference perl scalar. If it is C<1>, |
134 | which just means it contains a list of subvalues which this module will |
239 | then the value is "constructed" which just means it contains a list of |
135 | en-/decode as BER tuples themselves. |
240 | subvalues which this module will en-/decode as BER tuples themselves. |
136 | |
241 | |
137 | The I<DATA> value is either a reference to an array of further tuples (if |
242 | The I<DATA> value is either a reference to an array of further tuples |
138 | the value is I<CONSTRUCTED>), some decoded representation of the value, |
243 | (if the value is I<FLAGS>), some decoded representation of the value, if |
139 | if this module knows how to decode it (e.g. for the integer types above) |
244 | this module knows how to decode it (e.g. for the integer types above) or |
140 | or a binary string with the raw octets if this module doesn't know how to |
245 | a binary string with the raw octets if this module doesn't know how to |
141 | interpret the namespace/tag. |
246 | interpret the namespace/tag. |
142 | |
247 | |
143 | Thus, you can always decode a BER data structure and at worst you get a |
248 | Thus, you can always decode a BER data structure and at worst you get a |
144 | string in place of some nice decoded value. |
249 | string in place of some nice decoded value. |
145 | |
250 | |
146 | See the SYNOPSIS for an example of such an encoded tuple representation. |
251 | See the SYNOPSIS for an example of such an encoded tuple representation. |
|
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252 | |
|
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253 | =head2 DECODING AND ENCODING |
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254 | |
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255 | =over |
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256 | |
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257 | =item $tuple = ber_decoded $bindata[, $profile] |
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258 | |
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259 | Decodes binary BER data in C<$bindata> and returns the resulting BER |
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260 | tuple. Croaks on any decoding error, so the returned C<$tuple> is always |
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261 | valid. |
|
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262 | |
|
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263 | How tags are interpreted is defined by the second argument, which must |
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264 | be a C<Convert::BER::XS::Profile> object. If it is missing, the default |
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265 | profile will be used (C<$Convert::BER::XS::DEFAULT_PROFILE>). |
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266 | |
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267 | In addition to rolling your own, this module provides a |
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268 | C<$Convert::BER::XS::SNMP_PROFILE> that knows about the additional SNMP |
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269 | types. |
|
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270 | |
|
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271 | Example: decode a BER blob using the default profile - SNMP values will be |
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272 | decided as raw strings. |
|
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273 | |
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274 | $tuple = ber_decode $data; |
|
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275 | |
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276 | Example: as above, but use the provided SNMP profile. |
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277 | |
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278 | $tuple = ber_encode $data, $Convert::BER::XS::SNMP_PROFILE; |
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279 | |
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280 | =item $bindata = ber_encode $tuple[, $profile] |
|
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281 | |
|
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282 | Encodes the BER tuple into a BER/DER data structure. AS with |
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283 | Cyber_decode>, an optional profile can be given. |
|
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284 | |
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285 | The encoded data should be both BER and DER ("shortest form") compliant |
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286 | unless the input says otherwise (e.g. it uses constructed strings). |
|
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287 | |
|
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288 | =back |
|
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289 | |
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290 | =head2 HELPER FUNCTIONS |
|
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291 | |
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292 | Working with a 4-tuple for every value can be annoying. Or, rather, I<is> |
|
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293 | annoying. To reduce this a bit, this module defines a number of helper |
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294 | functions, both to match BER tuples and to construct BER tuples: |
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295 | |
|
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296 | =head3 MATCH HELPERS |
|
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297 | |
|
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298 | These functions accept a BER tuple as first argument and either partially |
|
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299 | or fully match it. They often come in two forms, one which exactly matches |
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300 | a value, and one which only matches the type and returns the value. |
|
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301 | |
|
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302 | They do check whether valid tuples are passed in and croak otherwise. As |
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303 | a ease-of-use exception, they usually also accept C<undef> instead of a |
|
|
304 | tuple reference, in which case they silently fail to match. |
|
|
305 | |
|
|
306 | =over |
|
|
307 | |
|
|
308 | =item $bool = ber_is $tuple, $class, $tag, $constructed, $data |
|
|
309 | |
|
|
310 | This takes a BER C<$tuple> and matches its elements against the provided |
|
|
311 | values, all of which are optional - values that are either missing or |
|
|
312 | C<undef> will be ignored, the others will be matched exactly (e.g. as if |
|
|
313 | you used C<==> or C<eq> (for C<$data>)). |
|
|
314 | |
|
|
315 | Some examples: |
|
|
316 | |
|
|
317 | ber_is $tuple, ASN_UNIVERSAL, ASN_SEQUENCE, 1 |
|
|
318 | orf die "tuple is not an ASN SEQUENCE"; |
|
|
319 | |
|
|
320 | ber_is $tuple, ASN_UNIVERSAL, ASN_NULL |
|
|
321 | or die "tuple is not an ASN NULL value"; |
|
|
322 | |
|
|
323 | ber_is $tuple, ASN_UNIVERSAL, ASN_INTEGER, 0, 50 |
|
|
324 | or die "BER integer must be 50"; |
|
|
325 | |
|
|
326 | =item $seq = ber_is_seq $tuple |
|
|
327 | |
|
|
328 | Returns the sequence members (the array of subvalues) if the C<$tuple> is |
|
|
329 | an ASN SEQUENCE, i.e. the C<BER_DATA> member. If the C<$tuple> is not a |
|
|
330 | sequence it returns C<undef>. For example, SNMP version 1/2c/3 packets all |
|
|
331 | consist of an outer SEQUENCE value: |
|
|
332 | |
|
|
333 | my $ber = ber_decode $snmp_data; |
|
|
334 | |
|
|
335 | my $snmp = ber_is_seq $ber |
|
|
336 | or die "SNMP packet invalid: does not start with SEQUENCE"; |
|
|
337 | |
|
|
338 | # now we know $snmp is a sequence, so decode the SNMP version |
|
|
339 | |
|
|
340 | my $version = ber_is_int $snmp->[0] |
|
|
341 | or die "SNMP packet invalid: does not start with version number"; |
|
|
342 | |
|
|
343 | =item $bool = ber_is_int $tuple, $int |
|
|
344 | |
|
|
345 | Returns a true value if the C<$tuple> represents an ASN INTEGER with |
|
|
346 | the value C<$int>. |
|
|
347 | |
|
|
348 | =item $int = ber_is_int $tuple |
|
|
349 | |
|
|
350 | Returns true (and extracts the integer value) if the C<$tuple> is an |
|
|
351 | C<ASN_INTEGER>. For C<0>, this function returns a special value that is 0 |
|
|
352 | but true. |
|
|
353 | |
|
|
354 | =item $bool = ber_is_oid $tuple, $oid_string |
|
|
355 | |
|
|
356 | Returns true if the C<$tuple> represents an ASN_OBJECT_IDENTIFIER |
|
|
357 | that exactly matches C<$oid_string>. Example: |
|
|
358 | |
|
|
359 | ber_is_oid $tuple, "1.3.6.1.4" |
|
|
360 | or die "oid must be 1.3.6.1.4"; |
|
|
361 | |
|
|
362 | =item $oid = ber_is_oid $tuple |
|
|
363 | |
|
|
364 | Returns true (and extracts the OID string) if the C<$tuple> is an ASN |
|
|
365 | OBJECT IDENTIFIER. Otherwise, it returns C<undef>. |
|
|
366 | |
|
|
367 | =back |
|
|
368 | |
|
|
369 | =head3 CONSTRUCTION HELPERS |
|
|
370 | |
|
|
371 | =over |
|
|
372 | |
|
|
373 | =item $tuple = ber_int $value |
|
|
374 | |
|
|
375 | Constructs a new C<ASN_INTEGER> tuple. |
|
|
376 | |
|
|
377 | =back |
147 | |
378 | |
148 | =head2 RELATIONSHIP TO L<Convert::BER> and L<Convert::ASN1> |
379 | =head2 RELATIONSHIP TO L<Convert::BER> and L<Convert::ASN1> |
149 | |
380 | |
150 | This module is I<not> the XS version of L<Convert::BER>, but a different |
381 | This module is I<not> the XS version of L<Convert::BER>, but a different |
151 | take at doing the same thing. I imagine this module would be a good base |
382 | take at doing the same thing. I imagine this module would be a good base |
… | |
… | |
159 | use common::sense; |
390 | use common::sense; |
160 | |
391 | |
161 | use XSLoader (); |
392 | use XSLoader (); |
162 | use Exporter qw(import); |
393 | use Exporter qw(import); |
163 | |
394 | |
|
|
395 | our $VERSION; |
|
|
396 | |
|
|
397 | BEGIN { |
164 | our $VERSION = '0.0'; |
398 | $VERSION = 0.8; |
165 | |
|
|
166 | XSLoader::load __PACKAGE__, $VERSION; |
399 | XSLoader::load __PACKAGE__, $VERSION; |
|
|
400 | } |
167 | |
401 | |
168 | our %EXPORT_TAGS = ( |
402 | our %EXPORT_TAGS = ( |
|
|
403 | const_index => [qw( |
|
|
404 | BER_CLASS BER_TAG BER_FLAGS BER_DATA |
|
|
405 | )], |
169 | const => [qw( |
406 | const_asn => [qw( |
170 | BER_CLASS BER_TAG BER_CONSTRUCTED BER_DATA |
|
|
171 | |
|
|
172 | ASN_BOOLEAN ASN_INTEGER32 ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER ASN_TAG_BER ASN_TAG_MASK |
407 | ASN_BOOLEAN ASN_INTEGER ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER |
173 | ASN_CONSTRUCTED ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE ASN_CLASS_MASK ASN_CLASS_SHIFT |
408 | ASN_OBJECT_DESCRIPTOR ASN_OID ASN_EXTERNAL ASN_REAL ASN_SEQUENCE ASN_ENUMERATED |
174 | ASN_SEQUENCE |
409 | ASN_EMBEDDED_PDV ASN_UTF8_STRING ASN_RELATIVE_OID ASN_SET ASN_NUMERIC_STRING |
175 | |
410 | ASN_PRINTABLE_STRING ASN_TELETEX_STRING ASN_T61_STRING ASN_VIDEOTEX_STRING ASN_IA5_STRING |
|
|
411 | ASN_ASCII_STRING ASN_UTC_TIME ASN_GENERALIZED_TIME ASN_GRAPHIC_STRING ASN_VISIBLE_STRING |
|
|
412 | ASN_ISO646_STRING ASN_GENERAL_STRING ASN_UNIVERSAL_STRING ASN_CHARACTER_STRING ASN_BMP_STRING |
|
|
413 | |
|
|
414 | ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE |
|
|
415 | )], |
|
|
416 | const_ber_type => [qw( |
|
|
417 | BER_TYPE_BYTES BER_TYPE_UTF8 BER_TYPE_UCS2 BER_TYPE_UCS4 BER_TYPE_INT |
|
|
418 | BER_TYPE_OID BER_TYPE_RELOID BER_TYPE_NULL BER_TYPE_BOOL BER_TYPE_REAL |
|
|
419 | BER_TYPE_IPADDRESS BER_TYPE_CROAK |
|
|
420 | )], |
|
|
421 | const_snmp => [qw( |
176 | SNMP_IPADDRESS SNMP_COUNTER32 SNMP_UNSIGNED32 SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64 |
422 | SNMP_IPADDRESS SNMP_COUNTER32 SNMP_UNSIGNED32 SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64 |
177 | )], |
423 | )], |
|
|
424 | decode => [qw( |
|
|
425 | ber_decode |
|
|
426 | ber_is ber_is_seq ber_is_int ber_is_oid |
|
|
427 | )], |
178 | encode => [qw( |
428 | encode => [qw( |
179 | ber_decode |
|
|
180 | ber_is ber_is_seq ber_is_i32 ber_is_oid |
|
|
181 | )], |
|
|
182 | decode => [qw( |
|
|
183 | ber_encode |
429 | ber_encode |
|
|
430 | ber_int |
184 | )], |
431 | )], |
185 | ); |
432 | ); |
186 | |
433 | |
187 | our @EXPORT_OK = map @$_, values %EXPORT_TAGS; |
434 | our @EXPORT_OK = map @$_, values %EXPORT_TAGS; |
188 | |
435 | |
189 | $EXPORT_TAGS{all} = \@EXPORT_OK; |
436 | $EXPORT_TAGS{all} = \@EXPORT_OK; |
|
|
437 | $EXPORT_TAGS{const} = [map @{ $EXPORT_TAGS{$_} }, qw(const_index const_asn)]; |
|
|
438 | |
|
|
439 | =head1 PROFILES |
|
|
440 | |
|
|
441 | While any BER data can be correctly encoded and decoded out of the box, it |
|
|
442 | can be inconvenient to have to manually decode some values into a "better" |
|
|
443 | format: for instance, SNMP TimeTicks values are decoded into the raw octet |
|
|
444 | strings of their BER representation, which is quite hard to decode. With |
|
|
445 | profiles, you can change which class/tag combinations map to which decoder |
|
|
446 | function inside C<ber_decode> (and of course also which encoder functions |
|
|
447 | are used in C<ber_encode>). |
|
|
448 | |
|
|
449 | This works by mapping specific class/tag combinations to an internal "ber |
|
|
450 | type". |
|
|
451 | |
|
|
452 | The default profile supports the standard ASN.1 types, but no |
|
|
453 | application-specific ones. This means that class/tag combinations not in |
|
|
454 | the base set of ASN.1 are decoded into their raw octet strings. |
|
|
455 | |
|
|
456 | C<Convert::BER::XS> defines two profile variables you can use out of the box: |
|
|
457 | |
|
|
458 | =over |
|
|
459 | |
|
|
460 | =item C<$Convert::BER::XS::DEFAULT_PROFILE> |
|
|
461 | |
|
|
462 | This is the default profile, i.e. the profile that is used when no |
|
|
463 | profile is specified for de-/encoding. |
|
|
464 | |
|
|
465 | You can modify it, but remember that this modifies the defaults for all |
|
|
466 | callers that rely on the default profile. |
|
|
467 | |
|
|
468 | =item C<$Convert::BER::XS::SNMP_PROFILE> |
|
|
469 | |
|
|
470 | A profile with mappings for SNMP-specific application tags added. This is |
|
|
471 | useful when de-/encoding SNMP data. |
|
|
472 | |
|
|
473 | Example: |
|
|
474 | |
|
|
475 | $ber = ber_decode $data, $Convert::BER::XS::SNMP_PROFILE; |
|
|
476 | |
|
|
477 | =back |
|
|
478 | |
|
|
479 | =head2 The Convert::BER::XS::Profile class |
|
|
480 | |
|
|
481 | =over |
|
|
482 | |
|
|
483 | =item $profile = new Convert::BER::XS::Profile |
|
|
484 | |
|
|
485 | Create a new profile. The profile will be identical to the default |
|
|
486 | profile. |
|
|
487 | |
|
|
488 | =item $profile->set ($class, $tag, $type) |
|
|
489 | |
|
|
490 | Sets the mapping for the given C<$class>/C<$tag> combination to C<$type>, |
|
|
491 | which must be one of the C<BER_TYPE_*> constants. |
|
|
492 | |
|
|
493 | Note that currently, the mapping is stored in a flat array, so large |
|
|
494 | values of C<$tag> will consume large amounts of memory. |
|
|
495 | |
|
|
496 | Example: |
|
|
497 | |
|
|
498 | $profile = new Convert::BER::XS::Profile; |
|
|
499 | $profile->set (ASN_APPLICATION, SNMP_COUNTER32, BER_TYPE_INT); |
|
|
500 | $ber = ber_decode $data, $profile; |
|
|
501 | |
|
|
502 | =item $type = $profile->get ($class, $tag) |
|
|
503 | |
|
|
504 | Returns the BER type mapped to the given C<$class>/C<$tag> combination. |
|
|
505 | |
|
|
506 | =back |
|
|
507 | |
|
|
508 | =head2 BER TYPES |
|
|
509 | |
|
|
510 | This lists the predefined BER types - you can map any C<CLASS>/C<TAG> |
|
|
511 | combination to any C<BER_TYPE_*>. |
|
|
512 | |
|
|
513 | =over |
|
|
514 | |
|
|
515 | =item C<BER_TYPE_BYTES> |
|
|
516 | |
|
|
517 | The raw octets of the value. This is the default type for unknown tags and |
|
|
518 | de-/encodes the value as if it were an octet string, i.e. by copying the |
|
|
519 | raw bytes. |
|
|
520 | |
|
|
521 | =item C<BER_TYPE_UTF8> |
|
|
522 | |
|
|
523 | Like C<BER_TYPE_BYTES>, but decodes the value as if it were a UTF-8 string |
|
|
524 | (without validation!) and encodes a perl unicode string into a UTF-8 BER |
|
|
525 | string. |
|
|
526 | |
|
|
527 | =item C<BER_TYPE_UCS2> |
|
|
528 | |
|
|
529 | Similar to C<BER_TYPE_UTF8>, but treats the BER value as UCS-2 encoded |
|
|
530 | string. |
|
|
531 | |
|
|
532 | =item C<BER_TYPE_UCS4> |
|
|
533 | |
|
|
534 | Similar to C<BER_TYPE_UTF8>, but treats the BER value as UCS-4 encoded |
|
|
535 | string. |
|
|
536 | |
|
|
537 | =item C<BER_TYPE_INT> |
|
|
538 | |
|
|
539 | Encodes and decodes a BER integer value to a perl integer scalar. This |
|
|
540 | should correctly handle 64 bit signed and unsigned values. |
|
|
541 | |
|
|
542 | =item C<BER_TYPE_OID> |
|
|
543 | |
|
|
544 | Encodes and decodes an OBJECT IDENTIFIER into dotted form without leading |
|
|
545 | dot, e.g. C<1.3.6.1.213>. |
|
|
546 | |
|
|
547 | =item C<BER_TYPE_RELOID> |
|
|
548 | |
|
|
549 | Same as C<BER_TYPE_OID> but uses relative object identifier |
|
|
550 | encoding: ASN.1 has this hack of encoding the first two OID components |
|
|
551 | into a single integer in a weird attempt to save an insignificant amount |
|
|
552 | of space in an otherwise wasteful encoding, and relative OIDs are |
|
|
553 | basically OIDs without this hack. The practical difference is that the |
|
|
554 | second component of an OID can only have the values 1..40, while relative |
|
|
555 | OIDs do not have this restriction. |
|
|
556 | |
|
|
557 | =item C<BER_TYPE_NULL> |
|
|
558 | |
|
|
559 | Decodes an C<ASN_NULL> value into C<undef>, and always encodes a |
|
|
560 | C<ASN_NULL> type, regardless of the perl value. |
|
|
561 | |
|
|
562 | =item C<BER_TYPE_BOOL> |
|
|
563 | |
|
|
564 | Decodes an C<ASN_BOOLEAN> value into C<0> or C<1>, and encodes a perl |
|
|
565 | boolean value into an C<ASN_BOOLEAN>. |
|
|
566 | |
|
|
567 | =item C<BER_TYPE_REAL> |
|
|
568 | |
|
|
569 | Decodes/encodes a BER real value. NOT IMPLEMENTED. |
|
|
570 | |
|
|
571 | =item C<BER_TYPE_IPADDRESS> |
|
|
572 | |
|
|
573 | Decodes/encodes a four byte string into an IPv4 dotted-quad address string |
|
|
574 | in Perl. Given the obsolete nature of this type, this is a low-effort |
|
|
575 | implementation that simply uses C<sprintf> and C<sscanf>-style conversion, |
|
|
576 | so it won't handle all string forms supported by C<inet_aton> for example. |
|
|
577 | |
|
|
578 | =item C<BER_TYPE_CROAK> |
|
|
579 | |
|
|
580 | Always croaks when encountered during encoding or decoding - the |
|
|
581 | default behaviour when encountering an unknown type is to treat it as |
|
|
582 | C<BER_TYPE_BYTES>. When you don't want that but instead prefer a hard |
|
|
583 | error for some types, then C<BER_TYPE_CROAK> is for you. |
|
|
584 | |
|
|
585 | =back |
|
|
586 | |
|
|
587 | =cut |
|
|
588 | |
|
|
589 | our $DEFAULT_PROFILE = new Convert::BER::XS::Profile; |
|
|
590 | our $SNMP_PROFILE = new Convert::BER::XS::Profile; |
|
|
591 | |
|
|
592 | # additional SNMP application types |
|
|
593 | $SNMP_PROFILE->set (ASN_APPLICATION, SNMP_IPADDRESS , BER_TYPE_IPADDRESS); |
|
|
594 | $SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER32 , BER_TYPE_INT); |
|
|
595 | $SNMP_PROFILE->set (ASN_APPLICATION, SNMP_UNSIGNED32, BER_TYPE_INT); |
|
|
596 | $SNMP_PROFILE->set (ASN_APPLICATION, SNMP_TIMETICKS , BER_TYPE_INT); |
|
|
597 | $SNMP_PROFILE->set (ASN_APPLICATION, SNMP_OPAQUE , BER_TYPE_IPADDRESS); |
|
|
598 | $SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER64 , BER_TYPE_INT); |
|
|
599 | |
|
|
600 | $DEFAULT_PROFILE->_set_default; |
190 | |
601 | |
191 | 1; |
602 | 1; |
192 | |
603 | |
193 | =head2 BUGS / SHORTCOMINGs |
604 | =head2 LIMITATIONS/NOTES |
194 | |
605 | |
195 | This module does have a number of SNMPisms hardcoded, such as the SNMP |
606 | This module can only en-/decode 64 bit signed and unsigned integers, and |
196 | tags for Unsigned32 and so on. More configurability is needed, and, if |
607 | only when your perl supports those. |
197 | ever implemented, will come in a form similar to how L<JSON::XS> and |
608 | |
198 | L<CBOR::XS> respresent things, namely with an object-oriented interface. |
609 | This module does not generally care about ranges, i.e. it will happily |
|
|
610 | de-/encode 64 bit integers into an C<ASN_INTEGER> value, or a negative |
|
|
611 | number into an C<SNMP_COUNTER64>. |
|
|
612 | |
|
|
613 | OBJECT IDENTIFIEERs cannot have unlimited length, although the limit is |
|
|
614 | much larger than e.g. the one imposed by SNMP or other protocols,a nd is |
|
|
615 | about 4kB. |
|
|
616 | |
|
|
617 | Indefinite length encoding is not supported. |
|
|
618 | |
|
|
619 | Constructed strings are decoded just fine, but there should be a way to |
|
|
620 | join them for convenience. |
|
|
621 | |
|
|
622 | REAL values are not supported and will currently croak. |
|
|
623 | |
|
|
624 | This module has undergone little to no testing so far. |
|
|
625 | |
|
|
626 | =head2 ITHREADS SUPPORT |
|
|
627 | |
|
|
628 | This module is unlikely to work when the (officially discouraged) ithreads |
|
|
629 | are in use. |
199 | |
630 | |
200 | =head1 AUTHOR |
631 | =head1 AUTHOR |
201 | |
632 | |
202 | Marc Lehmann <schmorp@schmorp.de> |
633 | Marc Lehmann <schmorp@schmorp.de> |
203 | http://software.schmorp.de/pkg/Convert-BER-XS |
634 | http://software.schmorp.de/pkg/Convert-BER-XS |